Abstract: ObjectiveTo investigate the relationship between the degenerative mechanisms of lumbar intervertebral disc (LID) and apoptosis.MethodsThe total RNAs were isolated from human LID tissues. Both the mRNAs from the degeneration and normal LID were reversely transcribed to the cDNAs. The cDNAs were labeled with the incorporations of fluorescent dUTP, for preparing the hybridization probes. The mixed probes were then hybridized to the cDNA microarray. After high-stringent washing, the cDNA microarray was scanned for the fluorescent signals and analyzed by computer image analysis. The apoptotic status and the expression of Bcl-2 and Bax in 12 cases of degenerative LID and 10 cases of normal LID were detected with TdT-mediated dUTP-biotin nick end labeling (TUNEL) and immunohistochemistry methods.ResultsAmong the 4096 targets, there were 10 genes related to apoptosis. The expression related to Bax protein gene was up-regulated and it was down-regulated for Bcl-2 protein. In group of normal LID, the average apoptotic index (AI) was (24.897±3.620); percentage of Bcl-2 positive cells was (31.440±4.150)%; percentage of Bax positive cells was (29.372±2.588)%, average optical density (OD) values of positive particles were (0.183± 0.010 ), ( 0.203 ±0.012) and (0.169±0.005) respectively. In group of degenerative LID, the average AI was (49.232±3.440); percentage of Bcl-2 positive cells was (18.239±2.470)%; percentage of Bax positive cells was (52.349±3.764)%; average OD values of positive particles were (0.152±0.003), (0.310±0.008) and (0.262±0.014) respectively. There were significantly differences in AI and expressions of Bcl-2 and Bax proteins between normal LID and degenerative LID (P<0.05).ConclusionCell apoptosis plays an important role in the process of LID degeneration. Both Bcl-2 and Bax take part in the occurrence and progression of LID.

Key words: DNA microarray, gene expression pattern, intervertebral disc degeneration, apoptosis, Bcl-2, Bax, epithelial membrane protein (EMP)